The present invention relates to blends of Liquid Crystal Polymers (LCPs) with thermoplastics, and more particularly to blends of stretchable liquid crystal polymers with thermoplastics suitable for use in the production of a variety of oriented shaped articles including films, fibers, and blow molded forms.
Anisotropic melt-forming polymers, also known as liquid crystalline polymers or xe2x80x9cLCPsxe2x80x9d are well known in the art. LCPs exhibit a parallel ordering of molecular chains in the melt phase and are also termed xe2x80x9cthermotropicxe2x80x9d liquid crystal polymers. LCPs are known to have many excellent physical properties, such as higher tenacity and modulus, additionally, LCPs have good barrier resistance to many chemicals, gases and water vapor.
Blending LCPs with other thermoplastic polymers has been shown to improve some of the physical properties of the thermoplastic polymers, depending on process and rheological conditions. Furthermore, since LCPs have reduced viscosities in the melt phase, a LCP in a blend has importance as a processing flow aid for molding. Examples of blends of LCPs with thermoplastics are disclosed in U.S. Pat. Nos. 4,386,174; 4,433,083 and 4,489,190; the LCP components of such blends being polymers with highly ordered crystalline structures that, although drawable in the melt, generally lack the ability to be stretched to a significant degree at temperatures below the molten state. As used herein, liquid crystalline polymers with highly ordered crystalline structures that are not able to be stretched to a significant degree at temperatures below their molten state are referred to as xe2x80x9cconventional LCPsxe2x80x9d.
A problem frequently encountered with blends of conventional LCPs and thermoplastics is that the improvement of their physical properties may be hampered due to the incompatibility of the conventional LCPs with the post extrusion orientation techniques commonly utilized for many thermoplastic articles. This problem is believed to be due to poor adhesion between the conventional LCPs and the thermoplastics and the inability to stretch these LCPs at normal orientation conditions of many non-liquid crystal thermoplastics. Compatibilizers, such as those described in WO 93/24754 and WO 96/00752, have been known to improve properties of the blend, but even they are insufficient especially when the blends are used in oriented articles such as fiber or films formed by stretching because conventional LCP domains do not stretch at temperatures below their melting point. Fiber or film made from such blends and oriented at temperatures typically used to stretch non-liquid crystal thermoplastics, result in separation of the LCP from the thermoplastic matrix resulting in poorer physical properties such as break strain or toughness.
Therefore, it is an objective of the present invention to improve the physical properties of LCP/thermoplastic blends.
It is another object of the present invention to improve the physical properties of oriented articles made from LCP/thermoplastic blends.
The objects of the present invention are achieved by providing stretchable LCPs to be used in the LCP/thermoplastic blend. These stretchable LCPs can be stretched at the same temperature range as many of the non-liquid crystal thermoplastics commonly used in extrusion applications, e.g., the production of fibers, films, blow molded articles, and the like. During a post orientation process, such as fiber or film stretching, the stretchable LCP can stretch and deform along with the non-liquid crystal thermoplastic matrix, maintaining adhesion between the LCP domains and the thermoplastic matrix. It has been found that blends in accordance with the subject invention provide oriented articles, for example fibers, films and blow molded articles, having improved toughness compared to oriented articles made from blends of conventional LCPs and non-liquid crystal thermoplastics.
The present invention relates to a melt mixture of a stretchable LCP with a thermoplastic polymer resulting in a blend with improved physical properties as compared to a conventional LCP blend. In a further embodiment, this invention relates to blends of stretchable LCPs, and thermoplastics, wherein said stretchable LCPs are present in such blends in an amount of from about 1 to about 30 percent by weight, based on the total weight of the LCP and thermoplastic components thereof.
The extent to which a polymer can be stretched or drawn depends upon the temperature at which stretching occurs as well as the form and size of the material that is being stretched. In the present application, the term xe2x80x9cstretchablexe2x80x9d polymer means a polymer capable of being stretched to at least 100% elongation (i.e., at least 100% break strain) before the break or rupture, when spun into tapes and tested according to the Tape Stretching Procedure set forth below. Break strain or percent elongation is the final length (Lf) of the polymer after stretching minus the initial length (Li) before stretching divided by the initial length Li and multiplied by 100 (i.e., % elongation=[(Lfxe2x88x92Li)/Li)]xc3x97100). For a film or other flat articles, the percent elongation is measured by the initial and final areas of the article (i.e., % elongation=[(final areaxe2x80x94initial area)/initial area]xc3x97100).
Preferably, the stretchable LCPs of the present invention can be stretched to at least about 100%, 150%, 200% or even 500% elongation without tearing or breaking using the Tape Stretching Procedure set forth below.
The preferred stretchable LCPs of the present invention are, wholly aromatic LCPs. Examples of stretchable LCPs can be found in U.S. Pat. No. 5,656,714; U.S. application Ser. No.: 09/483,103, now U.S. Pat. No. 6,222,000; U.S. application Ser. No.: 09/484,120, now U.S. Pat. No. 6,132,884; U.S. application Ser. No 09/483,765, now U.S. Pat. No. 6,207,790; and copending U.S. application Ser. No. 09/783,057; all of which are herein incorporated by reference in their entirety.
Stretchable LCPs are included among LCPs comprised of recurring units I, II, III, IV and V, where recurring unit I is 
recurring unit II is: 
recurring unit III is: 
where Ar1 is selected from the group consisting of: 
and mixtures thereof;
recurring unit IV is:
xe2x80x94Oxe2x80x94Ar2xe2x80x94Xxe2x80x94xe2x80x83xe2x80x83IV 
where Ar2 is selected from the group consisting of: 
and mixtures thereof, and X is independently selected from the group consisting of O and NR2 where R2 is independently selected from the group consisting of hydrogen and a C1 to C6alkyl; and
recurring unit V is a formula selected from the group consisting of: 
and mixtures thereof, where R1 is independently selected from the group consisting of hydrogen and C1 to C6 alkyl. To be stretchable, such polymers are required to contain specific amounts of particular recurring units. For example, stretchable LCPs having such recurring units include polymers which consist essentially of recurring units I, II, III, IV, and V wherein:
recurring unit I is 
recurring unit II is: 
recurring unit III is: 
wherein Ar1 is selected from the group consisting of: 
and mixtures thereof;
recurring unit IV is:
xe2x80x94Oxe2x80x94Ar2xe2x80x94Xxe2x80x94
wherein Ar2 is selected from the group consisting of: 
and mixtures thereof, and X is independently selected from the group consisting of O and NR2 wherein R2 is independently selected from the group consisting of hydrogen and a C1 to C6 alkyl; and
recurring unit V is selected from the group consisting of: 
and mixtures thereof, wherein R1 is independently selected from the group consisting of hydrogen and C1 to C6 alkyl;
wherein recurring unit I is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit II is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit III is present in the polymer in an amount of from about 5 to about: 20 mole percent, recurring unit IV is present in the polymer in an amount of from about 5 to about 20 mole percent, and recurring unit V is present in the polymer in an amount of from about 7 to about 15 mole percent and wherein:
(a) recurring units I and II combined are present in the polymer in an amount of from about 50 to about 75 mole percent and
(b) the polymer contains at least about 5 mole percent of recurring units of the formula: 
xe2x80x83with the proviso that recurring unit II is present in the polymer in an amount of at least about 30 mole percent, if and when the polymer also contains: 
xe2x80x83in combination with a total from 0 to about 5 mole percent of units selected from the group consisting of units (Vb), (Ve) and (Vd) and mixtures thereof. Preferably, such polymers contain from about 20 to about 40 mole percent of recurring unit I, from about 20 to about 40 mole percent of recurring unit II, from about 10 to about 15 mole percent of recurring unit III, from about 10 to about 15 mole percent of recurring unit IV and from about 10 to about 15 mole percent of recurring unit V. Stretchable LCPs such as these are described in U.S. Pat. No. 6,222,000.
Other stretchable LCPs are polymers that consist essentially of recurring unit I, II, III, IV and V, wherein:
recurring unit I is 
recurring unit II is: 
recurring unit III is: 
wherein is Ar1 is selected from the group consisting of: 
and mixtures thereof;
recurring unit IV is:
xe2x80x94Oxe2x80x94Ar2xe2x80x94Xxe2x80x94xe2x80x83xe2x80x83IV 
wherein Ar2 is selected from the group consisting of: 
and mixtures thereof, and X is independently selected from the group
consisting of O and NR2 wherein R2 is independently selected from the group consisting of hydrogen and a C1 to C6 alkyl; and
recurring unit V is a dioxy unit of the formula: 
in combination with at least one additional unit selected from the group consisting of: 
wherein R1 is independently selected from the group consisting of hydrogen and C1 to C6 alkyl,
wherein recurring unit I is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit II is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit III is present in the polymer in an amount of from about 5 to about: 20 mole percent, recurring unit IV is present in the polymer in an amount of from about 5 to about 20 mole percent, and recurring unit V is present: in the polymer in an amount of from about 7 to about 15 mole percent and wherein:
(a) recurring units I and II combined are present in the polymer in an amount of from about 50 to about 75 mole percent and
(b) the polymer contains at least about 5 mole percent of recurring units of the formula: 
xe2x80x83with the proviso that recurring unit II is present in the polymer in an amount of at least about 30 mole percent, if and when unit (Vc) is also present and the units (Va), (Vb), (Vd), and (Ve) combined, constitute up to about 5 mole percent of the polymer. Preferably, such polymers contain from about 20 to about 40 mole percent of recurring unit I from about 20 to about 40 mole percent of recurring unit II, from about 10 to about 15 mole percent of recurring unit III, from about 10 to about 15 mole percent of recurring unit IV and from about 10 to about 15 mole percent of recurring unit V. Stretchable LCPs such as these are described in U.S. Pat. No. 6,132,884
Stretchable LCPs also include polymers consisting essentially of recurring units I, II, III, IV and V, wherein:
recurring unit I is 
recurring unit II is: 
recurring unit III is: 
wherein Ar1 is selected from the group consisting of: 
and mixtures thereof;
recurring unit IV is:
xe2x80x94Oxe2x80x94Ar2xe2x80x94Xxe2x80x94
wherein Ar2 is selected from the group consisting of: 
and mixtures thereof; and X is independently selected from the group consisting if O or NR2 wherein R2 is independently selected
from the group consisting of hydrogen and a C1, to C6 alkyl; and recurring unit V is: 
wherein recurring unit I is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit II is present in the polymer in an amount of from about 15 to about 60 mole percent, recurring unit III is present in the polymer in an amount of from about 5 to about 20 mole percent, recurring unit IV is present in the polymer from about 5 to about 20 mole percent and recurring unit V is present in the polymer in a n amount of from about 7 to about 15 mole percent; wherein:
(a) recurring units I and II combined are present in the polymer in an amount of from about 50 to about 75 mole percent and
(b) the polymer contains at least about 5 mole percent of recurring units of the formula: 
(c) a least a portion of recurring unit III is: 
Preferably, such polymers contain from about 20 to about 40 mole percent of recurring unit 1, from about 20 to about 40 mole percent of recurring unit II, from about 10 to about 15 mole percent of recurring unit III, from about 10 to about 15 mole percent of recurring unit IV and from about 10 to about 15 mole percent of recurring unit V. Stretchable LCPs such as these are described in U.S. Pat. No. 6,207,790.
Stretchable LCPs are also included among three monomer unit polymers consisting essentially of recurring units I, II, and V wherein
recurring unit I is: 
recurring unit II is: 
and recurring unit V is selected from the group consisting of: 
and mixtures thereof, where R1 is independently selected from the group consisting of hydrogen and C1 to C6 alkyl and where the polymer is stretchable.
Minor amounts of other units that provide ester or ester-amide linkages may be present provided, that such units, do not obviate the properties desired by this invention.
In one embodiment of the three monomer unit polymer, recurring unit I is present in an amount of about 15 to about 35 mole %, recurring unit II is present in an amount of from about 20 to about 55 mole %, preferably about 30 to about 50 mole % and recurring unit V is present in an amount of from about 12 to about 48 mole %, preferably from about 12 to about 25 mole %.
In another embodiment of the three monomer unit polymer, recurring unit I is present in an amount of about 10 to about 50 mole %, recurring unit II is present in an amount of from about 35 to about 55 mole % and recurring unit V is present in an amount of from about 12 to about 50 mole %, preferably about 12 to 25 mole %.
In yet another embodiment of the three monomer unit polymer, recurring unit I is present in an amount of about 10 to about 50 mole %, recurring unit II is present in an amount of from about 35 to about 45 mole % and recurring unit V is present in an amount of from about 8 to about 50 mole %.
The stretchable LCP polymers of the present invention may be blended with any suitable thermoplastic. Desirably, such thermoplastics are polymers that are not liquid crystalline in nature, i.e., xe2x80x9cnon-liquid crystal thermoplastic polymersxe2x80x9d. Examples of suitable thermoplastics that may be blended with the stretchable LCPs are polyethylene, polypropylene, polybutylene, polyimide, polyamide, poly(ethersulfone), poly(etherimide), poly(etherketone), polycarbonate, poly(ethylene terephthalate), poly(ethylene napthalate), poly(butylene terephthalate), poly(phenylene sulfide), ethylene vinyl acetate, ethylene vinyl alcohol, polyvinyl chloride, polyvinyl alcohol, polyoxymethylene, poly(etheretherketone), cyclic olefin copolymer, polycyclohexylene terephthalate, and polyarylate. For many extrusion applications, non-liquid crystal thermoplastics such as polyethylene, polypropylene, polybutylene, poly(ethylene terephthalate), polyamide, ethylene vinyl acetate, ethylene vinyl alcohol, and cyclic olefin copolymer are of particular interest, with polyethylene, polypropylene, and poly(ethylene terephthalate) being representative of polymers having widespread use in the production of fibers, films, blow molded containers and other oriented articles. In the practice of this invention, extrusion grade thermoplastics that are oriented at processing temperatures of from about 120xc2x0 C. to about 160xc2x0 C. are of particular interest.
The amount of stretchable LCP in the blend is preferably from about 1 to about 30 wt. %, more preferably from about 5 to about 20 wt. % and even more preferably from about 5 to about 15 wt. % based on the total weight of the stretchable LCP and thermoplastic. The amount of thermoplastic in the blend is preferably an amount of from about 70 to about 99 wt. %, preferably from 80 to about 95 wt. % and even more preferably from about 85 to about 95 wt. % based on the total weight of the stretchable LCP and thermoplastic.
In an embodiment of particular interest, the subject invention relates to a melt blend comprising:
(a) a stretchable liquid crystal polymer; and
(b) a non-liquid crystal thermoplastic polymer capable of being oriented at processing temperatures of from about 120xc2x0 C. to about 160xc2x0 C.,
wherein said liquid crystal polymer is present in the blend in an amount of from about 5 to about 15% by weight, based on the total weight of the stretchable liquid crystal polymer and the non-liquid crystal thermoplastic polymer components thereof.
Another component that may be added in the blend is a compatibilizer. The task of a compatibilizer is to achieve a more uniform dispersed blend such as by diminishing the surface tension and/or improving adhesion between the components. Any suitable compatibilizer may be used to achieve a uniform dispersed blend such as those described in WO 96/00752 and WO 93/24574, herein incorporated by reference. When present, the compatibilizer is typically used in an amount of from about 0.1 to about 30 weight percent, based on the total weight of the stretchable liquid crystal polymer and the thermoplastic polymer
Examples of suitable general classes of compatibilizers are: a polyester polyurethane, a polyether polyurethane, a polyester elastomer, a polyether elastomer, a polyamide, a polyether polyamide, a polyether polyimide, or a functionalized polyolefin, where said functionalized polyolefin comprises functional groups selected from the group consisting of: a carboxyl group and its esters, a carboxylic anhydride group, a glycidyl group, an alkoxysilane group and combinations thereof.
Examples of specific compatibilizers that may be used are ethylene-maleic anhydride copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl acrylate copolymer grafted with maleic anhydride, ethylene-methyl acrylate-maleic acid terpolymer, ethylene-glycidyl methacrylate copolymer, ethylene-methyl acrylate-glycidyl methacrylate terpolymer, ethylene-methyl methacrylate-acrylic acid terpolymer, ethylene-vinyl acetate copolymer, an alkoxysilane modified ethylene-ethylacrylate copolymer, ethylene-acrylic acid copolymer, and a blend of polypropylene grafted with maleic anhydride with a dimer based polyamide.
If desired, the blends may contain one or more additional optional components such as for example, anti-blocking agents, anti-static agents, antioxidants, blowing agents, crystallization agents, colorants, dyes, lubricants, processing aids, stabilizers, fillers, reinforcing agents, impact modifiers, mold release agents, pigments, UV resistant agents, antifogging agents, wetting agents, and the like. Although not typically present in blends used in the production of stretched articles, additives such as such as fillers, reinforcing agents impact modifiers, and mold release agents may be used in blends used in specialty blow molding and/or thermoforming applications.
Any suitable method may be used to produce the blends of the present invention. For example, conventional extrusion equipment such as single or twin screw extruders may be used to produce the stretchable LCP blends. It is preferred that the composition be well-dispersed in order to produce a blend with superior properties. Conditions that may affect the dispersion of the blend include equipment, processing temperatures, rotation speed of the screw, feed rate and throughput. It is well within one skilled in the art of polymer blending to optimize these variables in order to produce a well-dispersed blend. Typically, high shear screw configurations are used to produce well-dispersed blends. The ratio of the melt viscosity of the dispersed phase to the matrix phase of the blend is another key variable well known to affect physical properties. A close match of melt viscosity at the blend process temperature, close to a ratio of 1, tends to yield the finest dispersed domains in the blend resulting in improved properties. Finally, a masterbatch blending process is preferred for compositions at low levels of either LCP or thermoplastic to ensure there is excellent dispersion of reproducible quantities of each resin.
It should also be noted that the dispersion of the blend might be affected by the order in which the components are mixed. For example, a well-dispersed blend may result when the polymer components are mixed first, and a compatibilizer is added later. Other times, a well-dispersed blend is produced when a portion of a compatibilizer is first blended together with the polymer components and the remaining portion of the compatibilizer is added later.
One of the advantages of the stretchable LCP blends is in the end use applications such as fiber stretching, film orientation and thermoforming, wherein orientation of the resulting articles is achieved by stretching or drawing. Conventional thermoplastics that are not stretched or drawn tend to have poor physical properties such as low tenacity and modulus. These conventional thermoplastics must be heated above their glass transition temperature, and stretched in order to orient the polymers and improve their physical properties. The problem with blends of conventional LCPs and non-liquid crystal thermoplastics is that they do not stretch well at temperatures typically used for conventional thermoplastic orientation processes, (e.g., temperatures of from about 1200 to about 160xc2x0 C. for polyolefins and poly(alkylene terephthalates). Conventional LCP domains in thermoplastic blends, when stretched below their melting point, may result in separation between the thermoplastic matrix and LCP domains and poor stretching performance for the blend as a whole. Although not wishing to be bound by any theory, it is believed that these separated domains diminish the physical properties of oriented articles made from blends of conventional LCPs and thermoplastics.
The blends containing stretchable LCPs have an advantage over blends containing conventional LCPs because they can be stretched at temperatures used for conventional thermoplastic orientation. Although not wishing to be bound by any theory, it is believed that stretchable LCP domains are less likely to separate from the thermoplastic matrix when the blend is stretched, resulting in better physical properties. In addition, fine fibrillar LCP domains in a fiber are further elongated during fiber orientation and LCP domains in a film can be biaxially oriented into a preferred platelet geometry during a film biaxial orientation process to further improve properties.
The stretchable LCP blend of the present invention may be processed into various shaped articles by known conventional thermoplastic processes. Shaped articles are any type of articles or parts formed by conventional processes, including but not limited to injection molding, co-extrusion, extrusion blow molding, stretch blow molding, biaxial stretch blow molding, vacuum forming, compression molding, dry lamination, sandwich lamination, thermoforming, fiber spinning, or combinations thereof. Desirably, articles made from the blend of the present invention may be stretched to at least 100% elongation, preferably at least 200% elongation when stretched at a normal processing temperature of the thermoplastic component thereof.
The blends are particularly suited for forming sheets and films because of their ability to be heat stretched at temperatures used for conventional thermoplastics. Hollow shaped articles such as containers (e.g., bottles, bags, tanks, packages and the like) may be produced by extrusion blow molding, direct blowing, injection blow molding, biaxial stretch blow molding or the like processes.
The stretchable LCP blends may also be laminated with thermoplastics such as polyolefins (e.g., polyethylene and polypropylene), polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate), and polyamides (e.g., nylon) to form multilayer films. Laminated films, sheets, tubes and the like may be produced by co-extrusion, dry lamination, sandwich lamination and like processes and laminated containers such as bottles, bags, tanks, and other like containers may be produced by blow molding, stretch blow molding, vacuum forming, compression molding or the like molding processes.
The LCP blends of the present invention have advantages over conventional LCP blends because of their ability to be stretched in combination with excellent gas barrier properties. The stretchable LCP blends are especially suitable for various packaging material and containers for which high oxygen barrier properties are required such as foods, medicines, cosmetics, textiles industrial chemicals, and the like.
Further, the stretchable LCP blends may also be used for producing fibers such as monofilaments, multifilaments and bicomponent fibers using conventional fiber forming equipment.
Particularly, the stretchable LCP blends may be used as at least one component in a bicomponent fiber because of their ability to be stretched at temperatures used for fiber stretching. Bicomponent fibers are well known and may be defined as a fiber having at least two distinct cross-sectional domains respectively formed from polymers having different relative viscosities. The distinct domains may be formed by at least two different polymers, or the same polymer class having different relative viscosities. Bicomponent fibers are intended to include, but are not limited to core and sheath fiber structures, side by side fiber structures, tipped fiber structures, micro-denier structures and mixed fiber structures. These types of Bicomponent fiber structures are described in U.S. Pat. No. 6,074,590, herein incorporated by reference.
In addition to the stretchable LCP blend, any type of fiber forming polymer may be used as a component in a bicomponent fiber. Suitable classes of polymers that may be used, include but are not limited to polyamides, polyesters, acrylics, and polyolefins. Specifically, nylon, low and high density polyethylene, polypropylene and polyethylene terephthalate may be employed as one of the components in a bicomponent fiber.
The bicomponent fibers are spun using conventional fiber-forming processes and equipment such as those described in U.S. Pat. Nos. 6,074,590; 5,948,528; 5,618,479; 5,162,074; 5,125,818; 5,344,297 and 5,445,884, herein incorporated by reference. Basically, spinning of bicomponent fibers involves coextrusion of the two or more components, (e.g., different polymers), to form several single filaments utilizing extrusion equipment to bring together the different components in a desired predetermined arrangement.
As mentioned previously, the stretchable LCP blends may be used as any component in the bicomponent fiber. For example, in a core and sheath fiber, the stretchable LCP blend could be used as either the core or the sheath component. One such example would have the stretchable liquid crystal polymer blend as the core and polyethylene terephthalate as the sheath. The stretchable LCP blend core component would contribute high modulus and tenacity as well as low elongation at room temperatures. Another example would have the stretchable LCP blend as the sheath and polyethylene terephthalate as the core to improve harsh environment capabilities because of the superior barrier properties of the stretchable LCP blend.
Tape Stretching Procedure
Polymers are melt spun into tapes using a Micromelt(trademark) apparatus. The apparatus is equipped with a 0.127 mm by 6.35 mm die. Melt temperatures typically vary between about 250-300xc2x0 C. depending upon the melt characteristics of the LCP sample. Throughput rates are 0.45 cc/min; take-up roller speeds are 2 rpm; and pack pressures typically range from about 100 kg/cm2 to about 290 kg/cm2, depending upon the Tg (or Tm) of the polymer. The resulting tapes will have an approximate thickness of 0.05 mm and a width of about 6 mm.
Test specimens for stretching should be 12.7 cm in length cut from each tape. Specimens are placed in a preheated Instron oven, allowed 6 minutes to come to temperature and then tested on an Instron type universal tester (equipped with a thermal chamber), set to a test temperature of 150xc2x0 C. (or a temperature 40xc2x0 C. above Tg for polymers for polymers having higher Tg values). The gauge length is set at 25 mm and the crosshead speed is set at 50.8 mm/min. The % break strain or the percent elongation is calculated at the break point.